docker-compose，無法在docker容器中打印環境變量

Question

我想打印 docker-compose 文件中定義的環境變量。

這是我docker-compose-1.yml ：

version: '3.6'

services:
  busybox:
    image: busybox
    command: 'echo $DEBUG'
    environment:
      - DEBUG='123456'

並且，嘗試在 docker 容器中打印DEBUG環境變量：

☁  environment-variables-in-compose [master] ⚡  docker-compose -f docker-compose-1.yml up
WARNING: The DEBUG variable is not set. Defaulting to a blank string.
Creating network "environmentvariablesincompose_default" with the default driver
Creating environmentvariablesincompose_busybox_1 ... done
Attaching to environmentvariablesincompose_busybox_1
busybox_1  |
environmentvariablesincompose_busybox_1 exited with code 0

如您所見，收到WARNING: The DEBUG variable is not set. Defaulting to a blank string. WARNING: The DEBUG variable is not set. Defaulting to a blank string.

我錯了嗎？

更新1：

docker-compose-1.yml ：

version: '3.6'

services:
  busybox:
    image: busybox
    command: 'echo $$DEBUG'
    environment:
      DEBUG: 123456

我使用雙$符號更改command ，但結果仍然不是我想要的。

☁  environment-variables-in-compose [master] ⚡  docker-compose -f docker-compose-1.yml up
Creating network "environmentvariablesincompose_default" with the default driver
Creating environmentvariablesincompose_busybox_1 ... done
Attaching to environmentvariablesincompose_busybox_1
busybox_1  | $DEBUG
environmentvariablesincompose_busybox_1 exited with code 0

如您所見，環境變量打印為$DEBUG ，而不是預期值123456

Answer 1

Compose 將從您運行 compose 的環境中擴展變量。 為擴大變量的容器內，躲避$使用$$ ：

command: '/bin/sh -c "echo $$DEBUG"'

有關更多詳細信息，請參閱： https : //docs.docker.com/compose/compose-file/#variable-substitution

編輯：我還在容器內添加了一個 shell 來擴展變量。